1. Field of the Invention
This invention relates to spandex comprising a polyurethane based on copoly(alkylene ethers) comprising tetramethylene ether and either ethylene ether or 1,2-propylene ether moieties in certain proportions.
2. Discussion of Background Art
Spandex can be prepared from a variety of polymeric glycols, diisocyanates, and difunctional chain extenders. The polymeric glycols used can be copolyethers, as disclosed in European Patent EP158,229 and EP004,356 and U.S. Pat. Nos. 4,224,432 and 4,658,065. However, spandex made from such copolyether glycols has an unsatisfactory combination of high set at low temperatures when unload power is adequate or low unload power when set is low, and improvements are still needed. Copolyethers are also disclosed in U.S. Pat. No. 3,425,999 and Japanese Patent Applications JP01-098624 and JP62-101622, but their use in making fibers is unknown.
The spandex of the present invention comprises a polyurethane reaction product of:
(A) a copoly(alkylene ether) glycol selected from the group consisting of poly(tetramethylene-co-ethylene ether) glycols wherein the ethylene ether moiety is present at about 15-37 mole % and poly(tetramethylene-co-1,2-propyleneether) glycols wherein the 1,2-propylene ether moiety is present at about 15-30 mole %, based on total alkylene ether moieties;
(B) a diisocyanate; and
(C) a chain extender selected from the group consisting of diamines and diols.
The process of the present invention comprises the steps of:
(A) contacting a copoly(alkylene ether) glycol selected from the group consisting of poly(tetramethylene-co-ethylene ether) glycols wherein the ethylene ether moiety is present at about 15-37 mole % and poly(tetramethylene-co-1,2-propyleneether) glycols wherein the 1,2-propylene ether moiety is present at about 15-30 mole %, based on total alkylene ether moieties with a diisocyanate to form a capped glycol;
(B) dissolving the capped glycol in a solvent;
(C) contacting the solution of the capped glycol formed in step (B) with a chain extender selected from the group consisting of diamines and diols to form a polyurethane spinning solution; and
(D) spinning the solution formed in step (C) to form the spandex.
It has now been found that spandex comprising polyurethanes derived from certain copoly(alkylene ether) glycols has a surprisingly good combination of high unload power (especially at low extensions) and low set (including at low temperatures, an advantage when fabrics comprising the spandex are used in winter) while retaining high elongation and heat-set efficiency.
As used herein, xe2x80x98spandexxe2x80x99 has its customary definition: a manufactured fiber in which the fiber-forming substance is a long chain synthetic polymer comprised of at least 85% by weight of a segmented polyurethane.
Fabrics are generally worn at relatively low elongations. Therefore, unload power at low fiber elongations (for example 30% and 60%) is important in uses such as tricot knits. When the spandex unload power is too low, the fabric knit from it has little or no sensible recovery power or restraining force. Similarly, low set is important so that after stretching the fabric can return to its intended dimensions without permanent distortion. The spandex of the invention can have an unload power at 30% elongation of at least 0.006 dN/tex, an unload power at 60% elongation of at least 0.012 dN/tex, and a set at xe2x88x925xc2x0 C. of not more than about 26%, the unload powers being measured after five 0-200% stretch and relax cycles, and the set being measured after five 0-300% stretch and relax cycles. It has now been found that when the amount of ethylene ether or 1,2-propylene ether moiety in the copoly(alkylene ether) glycol used in making the present spandex is too high, unload power at low elongations is unacceptably low, and set rises. When such ether moiety content is too low, it has little effect, and the set at low temperatures rises.
The copoly(alkylene ether) glycol can be a random copolyether, can be obtained by copolymerization of such a random copolyether with another polymeric glycol, or can be a mixture of such a random copolyether with another polymeric glycol. The copoly(alkylene ether) glycol used in the spandex of the invention can have a number-average molecular weight of about 1300-4500, more typically about 2000-3500.
Diisocyanates useful in making the polyurethane of which the present spandex is comprised include 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane, 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene, 1-isocyanato-2-[(4-isocyanato-phenyl)methyl]benzene, 1,1xe2x80x2-methylenebis(4-isocyanatocyclohexane), 4-methyl-1,3-phenylene-diisocyanate, and combinations thereof. 1-isocyanato4-[(4-isocyanato-phenyl)methyl]benzene (xe2x80x9cMDIxe2x80x9d) and mixtures thereof with 1-isocyanato-2-[(4-isocyanato-phenyl)methyl]benzene are preferred because of their ready commercial availability. The mole ratio of the diisocyanate(s) to the copoly(alkylene ether) glycol can be about 1.2-2.3.
Diol chain extenders useful in making the polyurethane used in the spandex of the invention include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,2-propylene glycol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-trimethylenediol, 2,2,4-trimethyl-1,5-pentanediol, 2-methyl-2-ethyl-1,3-propanediol, 1,4-bis(hydroxyethoxy)benzene, bis(hydroxyethylene) terephthalate, and mixtures thereof.
Use can be made of one, or a mixture of two or more, amine catalyst or organic metal catalyst in the preparation of the polyurethane. Illustrative examples of suitable amine catalysts include N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, triethylamine, N-methylmorpholine, N-ethylmorpholine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylenediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethyl-1,3-propanediamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylhexanediamine, bis-2-dimethylaminoethyl ether, N,N,Nxe2x80x2,Nxe2x80x2,Nxe2x80x2-pentamethyldiethylenetriamine, tetramethylguanidine, triethylenediamine, N,Nxe2x80x2-dimethylpiperazine, N-methyl-Nxe2x80x2-dimethylaminoethylpiperazine, N-(2-dimethylaminoethyl)morpholine, 1-methylimidazole, 1,2-dimethylimidazole, N,N-dimethylaminoethanol, N,N,Nxe2x80x2-trimethylaminoethyl ethanolamine, N-methyl-Nxe2x80x2-(2-hydroxyethyl)piperazine, 2,4,6-tris(dimethyl-aminomethyl)phenol, N,N-dimethylaminohexanol and triethanolamine. Suitable examples of organic metal catalysts include tin octanoate, dibutyltin dilaurate and dibutyllead octanoate.
Diamine chain extenders that can be used when a polyurethaneurea is desired as the fiber-forming substance of the spandex include hydrazine, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 2-methyl-1,5-pentanediamine, 1,2-diaminobutane, 1,3-diaminobutane, 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane, 2,2-dimethyl-1,3-diaminopropane, 1,3-diamino-2,2-dimethylbutane, 2,4-diamino-1-methylcyclohexane, 1,3-pentanediamine, hexamethylenediamine, 1,3-cyclohexanediamine, bis(4-aminophenyl)phosphine oxide, and mixtures thereof.
To control polyurethane molecular weight and the viscosity of a polyurethane spinning solution, a chain terminator such as n-butanol, diethylamine, cyclohexylamine, or n-hexylamine can be used, generally as a mixture with the chain extender. Small amounts of trifunctional materials such as diethylenetriamine and glycerol can also be used for polymer solution viscosity control.
Either melt polymerization or solution polymerization can be used. In the process of the invention solution polymerization is preferred for less thermal degradation of the polyurethane, especially when a polyurethaneurea is being prepared, since polyurethaneureas are generally too high melting to be prepared by melt polymerization. Useful solution polymerization methods include a xe2x80x9cone-shotxe2x80x9d method, in which each of the starting materials can be added to the solvent and dissolved and then heated to a suitable temperature and reacted so as to form the polyurethane, and a xe2x80x9cprepolymer methodxe2x80x9d. In the prepolymer method, a diisocyanate can be contacted with a copoly(alkylene ether) glycol to form an isocyanate-terminated prepolymer (a xe2x80x9ccappedxe2x80x9d glycol) which can then be dissolved in a solvent suitable for the final polyurethane. Examples of suitable solvents include dimethylacetamide (DMAC), dimethylformamide, dimethyl sulfoxide, and N-methyl-pyrrolidinone. The dissolved capped glycol can then be reacted with a diol to form a polyurethane or a diamine to form a polyurethaneurea. The prepolymer method is preferred for making polyurethaneureas, which generally dissolve with too much difficulty to be made readily by the one-shot method.
The spandex of the invention can also comprise additives such as UV absorbers, antioxidants, stabilizers against chlorine and gases, delustrants, and the like. Examples include a copolymer of diisopropylaminoethyl methacrylate and n-decyl methacrylate in a 75/25 weight ratio (Methacrol(copyright) 2138F, a registered trademark of E.I. du Pont de Nemours and Company), a condensation polymer of p-cresol and divinyl benzene (Methacrol(copyright) 2390 D, a registered trademark of E.I. du Pont de Nemours and Company), a polymer of bis(4-isocyanatocyclohexyl)methane and 3-t-butyl-3-aza-1,5-pentanediol (Methacrol(copyright) 2462B, a registered trademark of E.I. du Pont de Nemours and Company), poly(diethylaminoethyl methacrylate), hindered phenol-type agents such as 2,4,6-tris(2,6-dimethyl-4-t-butyl-3-hydroxybenzyl)isocyanurate (Cyanox(copyright) 1790, from Cytec Industries), 2,6-di-t-butyl-4-methylphenol, and Sumilizer GA-80 (produced by Sumitomo Chemical Co., Ltd.), nitrogen oxide scavengers such as HN-150 (Japan Hydrazine Co., Ltd.), UV stabilizers such as 2,4-di(2xe2x80x2,4xe2x80x2-dimethylphenyl)-6-(2xe2x80x3-hydroxy4xe2x80x3-n-octyloxyphenyl)-1,3,5-triazine (Cyasorb 1164D, from Cytec Industries), Sumisorb 300#622 (Sumitomo Chemical Co., Ltd.), benzotriazole-type agents such as various products available under the brand designation Tinuvin(copyright), phosphorus-containing agents such as Sumilizer P-16 (Sumitomo Chemical Co., Ltd.), hindered amine-type agents such as various products available under the Tinuvin(copyright) trademark, inorganic pigments such as titanium oxide, zinc oxide and carbon black, barium sulfate, metallic soaps such as magnesium stearate, mixtures of huntite and hydromagnesite (for example at 0.75 wt % based on weight of polyurethane), germicides containing silver, zinc or compounds thereof, deodorants, lubricants such as silicone and mineral oils, and antistatic agents such as cerium oxide, betaine and phosphorus-containing compounds. Any suitable method can be used for incorporating the additives into the polyurethane solution, for example, for uniform incorporation, as a solution or a slurry.
When wet- or dry-spinning are used to make the spandex, the just-spun filaments typically can be brought together, for example in an coalescence jet, to form a coalesced multifilament. The spinning speed can be 300-800 m/min or higher, and the circumferential speed ratio of the godet (feed) roll to that of the winder can be about 1.1-1.8. No particular limitations are imposed on the size or cross-sectional shape of the inventive spandex, which can, for example, have a round or flattened cross-section.
The spandex of the invention can be used alone or in combination with various other fibers in wovens, weft (including flat and circular) knits, warp knits, and personal hygiene apparel such as diapers. The spandex can be bare, covered, or entangled with a companion fiber, for example nylon, polyester, acetate, cotton, and the like.
Unless otherwise noted, physical characteristics of the spandex made in the Examples were measured as follows. An Instron 4502 tensile tester was used to determine tensile properties. Tenacity, elongation, and stress relaxation were measured at 22xc2x0 C. and, on a different sample, set was measured at xe2x88x925xc2x0 C. A 5-cm length (xe2x80x9cL1xe2x80x9d) of fiber was stretched to 300% elongation at a rate of 50 cm/min and allowed to relax. The stretch-and-relax cycle was repeated five times. Immediately after the fifth stretch, the stress at 300% elongation was recorded as xe2x80x9cG1xe2x80x9d. The fiber was held at 300% stretch for 30 seconds, and the resulting stress was recorded as xe2x80x9cG2xe2x80x9d. The fiber was allowed to relax a fifth time, and its length when the stress became zero was recorded as xe2x80x9cL2xe2x80x9d. The fiber was then stretched a sixth time until it broke. The tenacity when the yarn broke was recorded as xe2x80x9cG3xe2x80x9d, and the length of the specimen at the time of break was recorded as xe2x80x9cL3xe2x80x9d. The tenacity-at-break, elongation-at-break, stress relaxation, and set were determined using the following formulas:
Heat-set efficiency was measured by treating the yarn with 100xc2x0 C. steam in an unrestrained state for 10 minutes, after which it was treated with 100xc2x0 C. boiling water in an unrestrained state for 2 hours, then dried for one day at room temperature. Next, the yarn (length=L4) was extended 100% (length=2xc3x97L4), treated for 1 minute with 115xc2x0 C. steam at the extended length, after which it was dry heat-treated at 130xc2x0 C. at the same length, then left to stand one day at room temperature, again at the same length. The yarn was subsequently released from the extended state, and its final, relaxed length (xe2x80x9cL5xe2x80x9d) was measured. The heat-set efficiency was calculated as follows:
Heat-set efficiency (%)=100xc3x97(L5xe2x88x92L4)/L4
In all of the tests, at least three samples were tested and an average was calculated from the results. In the Tables, xe2x80x9cn.m.xe2x80x9d means not measured.
Unless otherwise noted, all Examples, except Example 5, had the following common elements: The mole ratios of ether moieties in the copolyether glycols are believed to be accurate within 15% relative; in Example 5, the mole ratios were accurate to less than about 5% relative. The mole ratio (capping ratio) of diisocyanate to polyether glycol was 1.64. An additive package of 2.2 wt % of a polymer of bis(4-isocyanatocyclohexyl)methane with 3-t-butyl-3-aza-1,5-pentanediol (Methacrol(copyright) 2462B) and 0.9 wt % of a condensation polymer of p-cresol and divinyl benzene (Methacrol 2390D) was added to the spinning solution; both weight percents were based on the total weight of the final fiber. Two filaments were dry-spun and coalesced to form a 20-decitex multifilament yarn.